In an apparatus for controlling opening/closing timings of intake/exhaust valves of an internal combustion engine, in order to improve responsiveness in phase conversion of a rotor member rotatable together with a cam shaft, relative to a housing member rotatable together with a drive member such as a crank shaft, there is known an apparatus having a torsion coil spring for urging the rotor member in a phase advancing direction relative to the housing member.
In this case, the torsion spring has one end thereof fixed to the housing member and the other end thereof fixed in a retaining groove defined in the cam shaft or the rotor member (see e.g. Patent Document 1).
Further, in an attempt to improve readiness of assembling of the valve opening/closing timing controlling apparatus to the engine, it has been contemplated to fix the torsion coil spring integrally to the apparatus to be handled together therewith, and it is conceivable to retain the other end of the torsion coil spring within the retaining groove formed in the rotor member. In this case, it is necessary to form the retaining groove deep enough to prevent inadvertent “spring-out” of the other end of the torsion coil spring from the retaining groove.
On the other hand, the end (the other end) of the torsion coil spring is moved in the direction of the depth of the retaining groove during an operation of the valve opening/closing timing controlling apparatus. Therefore, if the depth of the retaining groove is increased, this results in corresponding increase in the amount of movement, thus causing frictional wear, so that durability problem may arise.
Patent Document 1: Japanese Patent Application “Kokai” No. 11-223113